Process of producing phosphorus



a product in the Patented Aug. 12, 1939 mamas erases JOHN W. WALTON, OF ROCKDALE, TENNESSEE, ,ASSIGNOR TO TENNESSEE PRODUCTS CORPORATION, OF NASHVILLE, TENNESSEE, A CORPORATION OF TENNESSEE PROCESS OF PRODUCING PHOSPHORUS lilo Drawing.

This invention relates to improvements in processes for producing phosphorus and more particularly to a method of. recovering phosphorus from a blast furnace as a byproduction of ferro-phosphorus.

As well known to those skilled in the art, ferro-ghosphorus is an alloy of iron and phosp orus and is ordinarily produced by the treatment of phosphate rock, coke and iron expense and extensive equipment for the pur- Post6 bearing materials in a blast furnace. As is common in blast furnace operations, the raw materials are charged into the furnace and the ferro-phosphorus withdrawn periodically in amolten state along with slag, the gases passing out through a down-comer near the top of the furnace stack and utilized in generation of ower. These gases are known to contain p osphorus, which is capable of recovery, would prove to be a valuable by-product in. the production of ferro-phosphorus.

Attempts have been made to remove the phosphorous from the furnace gases-near the top of the furnace,-but these attempts have not been successful from a commercial standpoint owing to operating difiiculties encountered, such as the clogging or bridging over of the material at the top of the stack. Moreover, the gases near the top of the furnace areladen with impurities aside from containing relatively small quantities of phosphorus, with the result that if recovered in any appreciable amounts, it is generally accompanied by considerable quantities of these impurities which can only be removed at great The object of the present invention is, therefore, to provide an economical and commerically practical method of recovering-the phosphorus in relatively large quantities and n a relatively pure state from a blast furnace, and more especially as a by-product of ferrophosphorus production operations. The manner in which the operations are carried out will be understood from the following:

Experience in ferro-phosphorus blast furnace operations has led-to the conclusion that there exists two fairly well defined melting zones in the furnace,one in which the iron Application filed September22, 1827. Serial 1%:221301.

ore is smelted and another in which the phosphate rock melts or is fused. It has also been established thatthe phosphate rock requires a higher temperature for reduction than does the iron ore, and hence the meltin zone of the phosphate rock is below that o the iron ore, and. in the region adjacent the tuyeres where the maximum temperature is maintained. As well known in the blast furnace art, the tuyres are theopenings through which an air blast is admitted to the furnace, and are located in the lower portion of the stack but above the bottom thereof. Thus as the charge of raw materials ordinarily consisting of phosphate rock, iron-ore, coke and a flux, descends in the stack, the reduction of the iron oxide in the charge takes place at a higher level, but the phosphate rock, is not reduced until it reaches a lower level of high est temperature where itcomes into contact with the incandescent coke, thusliberating the phosphorus which is carried upwardly by the gases containing carbon monoxide and phosphorus. The ascending gases encounter the iron in the process of reduction in the upper parts of thestack whereupon the major portion of the phosphorus is absorbed and the remainder with the carbon monoxide passing on and upwardly to the top of the stack and thence to the down-comer. Hence as the gases reach a higher level, they become leaner in phosphorus content, until eventually they escape with little or no phosphorus. On the other hand, the gases at the'lower level of the stack are rich in phosphorus-and manifestly so, since thegases' have not had an opportunity to come in contact with the iron and thus be absorbed to form the phosphite of iron, or ferrophosphorus.

To carry out the process of recovering the phosphorus,therefore, I prefer-to withdraw the phosphorus bearing gases from the interior of the stack at a point orpoints in the however, it has been found that a somewhat more restricted zoneextending a short distance upwardly from the level of the tuyeres is the most satisfactory from an operating standpoint, as there are less slag accretlons to contend with and yet the gases in the region are sufficiently rich in phosphorus.

Any suitable means for withdrawing the gases from the furnace may be employed. the principal precaution to be observed being that of holding back the solid matter within the furnace while allowing the gas to pass into the pipes or passages provided for the removal of the gases. The general procedure in withdrawing the gases is to tap the furnace wall at the point or points selected and to allow the gas to escape under the pressure within the furnace. Practical furnace operators may readily devise suitable means for accomplishin this end.

The gases liaving been removed from the furnace are then treated, depending on the use to be made of .the phosphorus to be recovered. Such treatment would consist in general of a cooling the gas and condensing the phosphorus in several stages, as for 1nstance, by passing the gas from one body of water to another, until the phosphorus content of the gases has been entirely condensed. A suitable o crating equipment for this purpose would e a series of tanks filled with water, each having a discharge pipe near its top which enters the succeeding container below the water level thereof, and so on. Thus each container will condense a portion of the phosphorus in the gases until it has allbeen removed.

phosphorus Other means may also be emplo ed for recovering the phosphorus such as urn1ng the uncondense gas thereby converting the into phosphorus pentom'de (P 0 and finally converting the P 0 into phosphoric acid by treatment with water orwater vapor and the recovery of the phosphoric acid from the gases by passing the same through an electric precipitator, as for instance, of the Cottrell type. However, any suitable method of recovering the phosphorus or of treating the phosphorus thus recovered may be utilized without departing from the spirit of my invention.

It has also been observed that quantities of phosphorus liberated within the stack of the furnace, find their way through the brickwork lining of the stack extending up- 'wardly above the region of the tuyeres to the down-comer, and also penetrates the packing between the brickwork and the outer shell of the furnace. This phosphorus may also be removed from these portions of the stack aside from the regions immediately adjacent the tuyeres, and hence I do not wish to limit the invention to any specific region of removal, except perhapsat a level below the down-comer.

Having set forth a preferred method embodying my invention, I claim;

1. The process of recovering phosphorus from phosphorus bearing material which comprises charging a blast furnace with phosphorus containing, and carbonaceous materials, and reducing and iluxing agents, and maintaining a high temperature and free carbonaceous material in the reducing zone of the furnace to reduce the phosphorus containing material to gaseous condition withdrawing the gases directly from said reducing zone, and recovering the phosphorus content from said gases.

2. The process of recovering phosphorus from phosphorus bearing material which comprises charging a blast furnace with phosphorus containing materials, carbonaceous material and reducing and fluxing agents, maintaining a blast of heated air supply under pressure into the fusion zone of the furnace, to cause combustion of said carbonaceous material and produce and maintain a high temperature to enable the carbonaceous material to combine with the resulting phosphorus gaseous compounds to release their phosphorus content, withdrawing the resulting ases-directly from saitl reducing zone and recovering the phosphorus content therefrom.

3. The process of recovering phosphorus from phosphorus containing materials, which comprises charging a blast furnace with the phosphorus containing material and with car- 'bonaceous materials, and reducing and fluxing agents, maintaining a phosphorus reducing temperature in the fusion zone of the furnace, to generate gaseous phosphorus contaming com ounds and enable the same to combine wit 1 the carbonaceous material to release the phosphorus content thereof, then withdrawing the gases under pressure directly from the fusion zone of the furnace iftnd recovering the phosphorus content thererom.

4. The process of recovering. phosphorus from phosphorus containing materials, which comprises charging a blast furnace with the phosphorus containin material, and with carbonaceous materia s, and reducing and fluxing agents, maintaining a phosphorus reducing temperature in the fusion zone of the furnace to generate gaseous phosphorus containing compounds and enable the same to combine with the carbonaceous material to release the phosphorus content thereof, then withdrawing the gases under pressure directly from the fusion zone of the furnace, then cooling said gases and recovering therefrom the phosphorus content thereof.

5. The process of recovering phosphorus from phosphorus containing materials which comprises charging a blast furnace with the phosphorus containing material, carbon, silica and iron contaimng material, subjectmgjthe charged material to and maintaining a. h reducing temperature in fusion zone 

